Typical x-ray analytical instruments include an x-ray source and an x-ray optical system that provide an x-ray probe beam. Characteristics of the probe beam determine the characteristics and capabilities of the instrument. Performance parameters of the probe beam include divergence for spatial definition, bandwidth for energy definition, and intensity for a given cross section. These parameters, however, cannot be independently optimized, since improving one parameter often reduces the performance of the other parameters. Most x-ray probe beams use characteristic emission lines that result from the interaction between target atoms and accelerated electrons. The spectrum that an optical system can deliver is limited by the available spectrum from a specific target.
Current technologies in x-ray sources and x-ray optics cannot deliver an ideal probe beam, which has the attributes of absolute parallelism, very narrow energy bandwidth, variable wavelength, and very high intensity. Instead, different optical systems are constructed and arranged to deliver beams with different characteristics. Combined with different x-ray source designs, the optical systems deliver beams required for different instrument capabilities, functions, and applications. This approach usually involves multiple optical systems and even multiple x-ray tubes or multiple targets and, thus, is inconvenient to manage and is costly.
Some systems employ multilayer optics that include a bending mechanism to change the curvature of the multilayer optic for different wavelengths. Although such systems enable the use of different sources, mechanical systems which can reliably and accurately form a curvature matching a specific wavelength are difficult to fabricate. In addition, the multilayer optic which is designed to work with multiple wavelengths cannot be optimized for each specific wavelength.
These multilayer optic systems may also include multiple sections of optics in which each section is designed for a specific wavelength. The section of the optic is mechanically moved to the working position when a specific working wavelength is needed. However, these systems do not address issues associated with 2-dimensional cases.
Such multilayer optical systems further include multiple multilayer coating arrangements as a stack of structures, in which each structure is designed for a specific wavelength. Although these systems offer convenience and low cost, their performance is compromised because of the lower reflectivity for every specific wavelength and high background noise due to the Bragg reflections at different energies off different multilayer coating structures.
Other systems have been employed as 2-dimensional systems which include two 2-dimensional optics in a face-to-face arrangement. Each optic is designed for a different energy or wavelength. However, such an arrangement has one or both optics at a source take-off angle that is far from the ideal take-offs that are optimal for performance.
Even when the optics designed for the same energy, there might be a need for quickly changing the configuration among various beam configurations, such as parallel beam and focusing beam configurations.
Accordingly, a probe beam system which can deliver beams of different characteristics is needed.